NO sub(y) partitioning from measurements of nitrogen and hydrogen radicals in the upper troposphere

Recent studies using NO, NO sub(y), OH and HO sub(2) (HO sub(x)) observations have postulated acetone and convection of peroxides as significant sources of HO sub(x) in the upper troposphere (UT). This work focuses on the effect these additional HO sub(x) sources have on the modeled NO sub(y) partitioning and comparisons of the modeled NO sub(x)/NO sub(y) ratio to observations. The measured NO sub(x)/NO sub(y) ratio is usually much higher than predicted regardless of the presence of acetone in the model. The exception occurs for air parcels having low NO sub(y) and O sub(3) values. For these air parcels the measured NO sub(x)/NO sub(y) ratio is much lower than the calculated ratio unless acetone is included in the model. In all cases acetone increases the fraction of NO sub(y) that is peroxy acetyl nitrate (PAN) from typical values of much less than 0.1 to values as high as 0.35. Including acetone also reduces the scatter in a comparison between modeled and observed NO sub(x)/NO sub(y) ratios.